Dynamic cloning of application infrastructures

ABSTRACT

Techniques for dynamically cloning application infrastructures are provided. In one embodiment, a computer system can monitor one or more metrics pertaining to an infrastructure for an application at a first site. If the one or more metrics exceed or fall below one or more corresponding thresholds, the computer system can clone the infrastructure at a second site distinct from the first site, thereby enabling the application to be hosted at the second site.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit and priority under 35 U.S.C.119(e) of U.S. Provisional Application No. 61/895,762, filed Oct. 25,2013, entitled “VIP CLONING.” The entire contents of this provisionalapplication are incorporated herein by reference for all purposes.

BACKGROUND

“Pervasive computing,” which is the emerging trend of embeddingcomputing technology in commonly-used objects and environments, haschanged the way data is consumed and generated. For example, the myriadmobile and wearable computing devices available today (e.g.,smartphones, tablets, smartwatches, etc.) enable users to accessapplications and services, such as video streaming, blogging, socialnetworking, etc., around the clock and on the go.

While pervasive computing has clear benefits for end-users, it alsoincreases the burden on service providers that host theapplications/services being consumed. For instance, consider a socialnetworking application, or any other application that deals withuser-generated content. For this kind of application, a football game, aconcert, or a news event can cause a sudden spike in application trafficnear the event location due to, e.g., user posts, uploads of photosand/or videos of the event, and so on. Unfortunately, conventionalapproaches to application infrastructure management (which generallyrely on manual/static setup) do not allow service providers todynamically scale/adapt their server-side resources to meet the demandsof such bursty traffic. As a result, the application may fail or becomeless responsive in these (and other similar) scenarios.

SUMMARY

Techniques for dynamically cloning application infrastructures areprovided. In one embodiment, a computer system can monitor one or moremetrics pertaining to an infrastructure for an application at a firstsite. If the one or more metrics exceed or fall below one or morecorresponding thresholds, the computer system can clone theinfrastructure at a second site distinct from the first site, therebyenabling the application to be hosted at the second site.

The following detailed description and accompanying drawings provide abetter understanding of the nature and advantages of particularembodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a network environment according to an embodiment.

FIG. 2 depicts a flow in the network environment of FIG. 1 withoutapplication infrastructure (AI) cloning according to an embodiment.

FIG. 3 depicts a flow in the network environment of FIG. 1 with AIcloning according to an embodiment.

FIG. 4 depicts a flowchart that can be carried out by an applicationresource broker (ARB) for creating a cloned application infrastructureaccording to an embodiment.

FIG. 5 depicts a flowchart that can be carried out by an ARB for tearingdown a cloned application infrastructure according to an embodiment.

FIG. 6 depicts a computer system according to an embodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousexamples and details are set forth in order to provide an understandingof various embodiments. It will be evident, however, to one skilled inthe art that certain embodiments can be practiced without some of thesedetails, or can be practiced with modifications or equivalents thereof.

1. Overview

The present disclosure describes techniques, referred to collectively as“application infrastructure (AI) cloning,” for dynamically cloning aninfrastructure for an application in response to various criteria. Forexample, consider a scenario where an application A is hosted by aservice provider at a site S1. The infrastructure for application A atsite S1 may include a virtual server (identified by a virtual IP address(VIP)) that is configured to, e.g., receive and load balance clientrequests. The infrastructure may further include one or more applicationservers that are configured to execute the actual application andprocess client requests redirected by the virtual server.

Assume that application A experiences an unexpected spike in trafficthat causes the infrastructure at site S1 to become overloaded (or reacha state where it will soon be overloaded). For instance, the hardwarerunning the virtual server and/or the application servers may experiencehigh CPU or memory utilization, a large number of concurrentconnections, etc. Alternatively, assume that one or more of the hardwareand/or software components at site S1 fail. In either of thesesituations, AI cloning can be used to detect the load/failure conditionand automatically create a new infrastructure for application A atanother site S2 based on the existing infrastructure at site S1. Thisprocess can comprise, e.g., cloning the virtual server and applicationservers from site S1, such that the cloned versions are created onunused/excess hardware capacity at site S2. The new infrastructure atsite S2 can then take over a portion of the application processingpreviously handled by site S1, thereby reducing the load at site S1 andimproving overall application performance.

In certain embodiments, site S2 can be selected for hosting the newinfrastructure based on factors that are most likely to improve theperformance of application A. For example, in one embodiment, site S2can be selected based on its proximity to the clients accessingapplication A, which can reduce the latency experienced by the clients.

Further, in scenarios where the new infrastructure at site S2 wascreated due to high load at site S1, the AI cloning mechanism cancontinue monitoring the load at site S1 while site S2 is operational andhandling application requests. If the load at site S1 falls below apredefined threshold, the AI cloning mechanism can tear down the clonedinfrastructure at site S2, thereby freeing the associated hardwareresources so that they may be reused for other purposes (such assupporting new infrastructures for other applications).

These and other features of the present invention are described infurther detail in the sections that follow.

2. Exemplary Network Environment

FIG. 1 is a simplified block diagram of a network environment 100 inwhich AI cloning may be implemented according to an embodiment. Asshown, network environment 100 includes a number of clients 102, a site104, a management server 106, and a global server load balancer (GSLB)108. All of these entities are interconnected via a network 110, whichmay be a private network (e.g., a LAN), a public network (e.g., a WAN orthe Internet), or a combination of private and public networks.

Clients 102 are end-user computing devices, such as a desktop computer,a laptop computer, a personal digital assistant, a smartphone, a tablet,or the like. Clients 102 can each execute (via, e.g., a standard webbrowser or proprietary software) a client component of a distributedsoftware application, thereby enabling users of clients 102 touse/interact with the application.

Site 104 is a facility/location that houses various computer systemsoperated by a service provider, the IT department of anenterprise/organization, or some other entity. In a particularembodiment, site 104 can be a data center. Site 104 can provide anenvironment in which the server-side infrastructure components of adistributed software application can run. For instance, in the exampleof FIG. 1, site 104 includes an application delivery controller (ADC)112 comprising a virtual server 116 and a host system 114 comprisingapplication servers 118, 120, and 122. As known in the art, virtualserver 116 of ADC 112 can be associated with a virtual IP address (VIP)that is assigned to a particular application running on applicationservers 118-122. Upon receiving an application request packet directedto the VIP (from, e.g., a client 102), virtual server 116/ADC 112 canperform various Layer 4-7 functions with respect to the packet toenhance and/or accelerate the delivery of the application. For example,virtual server 116/ADC 112 can perform Layer 4-7 traffic redirection,server load balancing, automated failover, TCP connection multiplexing,server offload functions (e.g., SSL acceleration and TCP connectionmanagement), data compression, network address translation, and more.

Once virtual server 116/ADC 112 has completed its packet processing,virtual server 116 can forward the request packet to an appropriateapplication server 118, 120, or 122. The application server can thenhandle the request by executing the application and generating aresponse for transmission to the originating client. In the embodimentof FIG. 1, it is assumed that application servers 118, 120, and 122 runwithin virtual machines (VMs) hosted on host system 114. However, inalternative embodiments, application servers 118, 120, and 122 may rundirectly on non-virtualized hardware, such as separate physical serversystems.

Management server 106 is a computer system or collection/cluster ofcomputer systems that is configured to manage (via, e.g., an applicationresource broker (ARB) 124) the hardware and software resources of site104. In one embodiment, management server 106/ARB 124 can be maintainedby the same entity that operates site 104. Generally speaking, ARB 124can implement a policy engine for performing tasks such as managing thelifecycles of virtual server 116 and application servers 118, 120, and122, monitoring the health and/or capacity of ADC 112 and host system114, and so on. Additional details regarding the functions of ARB 124are disclosed in commonly-assigned U.S. patent application Ser. No.12/909,131, filed Oct. 21, 2010, entitled “METHOD AND APPARATUS FORPROVISIONING OF RESOURCES TO SUPPORT APPLICATIONS AND THEIR VARYINGDEMANDS,” which is incorporated herein by reference for all purposes.

Finally, GSLB 108 is a device/computer system that is configured to sitbetween clients 102 and one or more DNS servers (not shown). When aclient 102 submits a DNS request for a particular host name to a DNSserver, GSLB 108 can proxy the request and intelligently modify the IPaddress list returned by the DNS server in view of one or more rules. Inparticular, GSLB 108 can prioritize (i.e., place at the top of the list)the IP address that is likely to provide the “best” (e.g., fastestand/or most reliable) response to the client. GSLB 108 can then transmitthe modified list to the client, thereby causing the client to use the“best” IP address for communicating with the host. Additional detailsregarding the functionality of GSLB 108 are provided in, e.g.,commonly-assigned U.S. Pat. No. 8,024,441, filed Feb. 16, 2007, entitled“GLOBAL SERVER LOAD BALANCING,” which is incorporated herein byreference for all purposes.

It should be appreciated that network environment 100 is illustrativeand not intended to limit embodiments of the present invention. Forexample, the various entities depicted in network environment 100 mayhave other capabilities or include other subcomponents that are notspecifically described. One of ordinary skill in the art will recognizemany variations, modifications, and alternatives.

3. Flow without AI Cloning

To provide context for the embodiments described herein, FIG. 2 depictsan example of an application request flow 200 in network environment 100when AI cloning has not been implemented/enabled. Flow 200 assumes thatthe application being accessed (e.g., application A) is currently hostedat site 104.

Starting with step (1) (reference numeral 202), client 102 (which isaccessing application A for the first time) can send out a DNS requestin order to determine the IP address of the application. At step (2)(reference numeral 204), GSLB 108 can intercept the DNS request,communicate with a DNS server (not shown), and return a DNS responsethat includes the application's IP address to client 102. Sinceapplication A is being hosted at site 104, the IP address can correspondto the VIP of virtual server 116.

Upon receiving the DNS response, client 102 can transmit an applicationrequest packet to the VIP, which is received by virtual server 116 (step(3), reference numeral 206). Virtual server 116 can perform itsdesignated processing on the request packet (e.g., load balancing,compression, etc.) and redirect the packet to one of application servers118, 120, and 122 on host system 122 (step (4), reference numeral 208).The receiving application server can then process the request packet perthe logic of application A, generate a response, and cause the responseto be returned, either directly or through virtual server 116/ADC 112,to client 102 (not shown).

Concurrently with the steps above, ARB 124 of management server 106 canmonitor metrics with respect to ADC 112/virtual server 116 and/or hostsystem 114/application servers 118-122 (reference numeral 210). ARB 124can use these metrics to perform various management tasks, such asprovisioning/de-provisioning VMs on host system 114, device discovery,capacity/performance reporting, etc.

4. Flow with AI Cloning

As noted previously, one issue with relying on a single, or staticnumber, of site(s)/application infrastructure(s) for serving anapplication (such as application A in FIG. 2) is that the applicationservice provider may not be able to gracefully handle unexpected burstsin traffic, or scenarios where one or more software/hardware componentsat the site(s) experience failures. This, in turn, can cause theapplication to slow down or become unresponsive. To address these andother similar issues, FIG. 3 depicts a high-level flow 300 in networkenvironment 100 where the infrastructure for application A isdynamically cloned from existing site 104 to a new site (324) inresponse to conditions at the existing site.

Starting with step (1) (reference numeral 302), ARB 124 of managementserver 106 can monitor load and/or health metrics pertaining to ADC112/virtual server 116 and/or host system 114/application servers118-122 of site 104. For example, in one embodiment, ARB 124 can monitorthe number of concurrent connections to the VIP for virtual server 116.In another embodiment, ARB 124 can monitor the CPU or memory utilizationof ADC 112 or host system 114. In yet another embodiment, ARB 124 canmonitor the runtime status of the VMs executing application servers118-122, such as whether they are active (i.e., powered on), suspended,powered off, etc.

At step (2) (reference numeral 304), ARB 124 can detect, based on theload/health metrics monitored at step (1), that AI cloning should beperformed with respect to the infrastructure of application A. Thisdetection may be triggered by, e.g., determining that one or more of themetrics have exceeded (or fallen below) one or more predefinedthresholds specified in a user-defined policy.

In response to the detection at step (2), ARB 124 can cause theinfrastructure for application A at site 104 to be cloned to a new site324 (step (3), reference numeral 306). In a particular embodiment, thiscloning can comprise creating a new virtual server 330 (with a new VIP)at an ADC 326 of site 324 based on existing virtual server 116(reference numeral 308), as well as creating new application servers332, 334, and 336 at a host system 328 of site 324 based on existingapplication servers 118, 120, and 122 (reference numeral 310).

Further, in order to redirect client traffic to the new VIP at site 324,ARB 124 can send a notification to GSLB 108 that identifies the new VIPas being associated with application A. This notification can includethe new VIP and the application's host name. GSLB 108 can then add thenew VIP to a list of IP addresses for the application.

Turning now to the application request flow, at step (5) (referencenumeral 316), client 102 can send out a DNS request for resolving the IPaddress of application A. At step (6) (reference numeral 318), GSLB 108can intercept the request and return a DNS response that include the newVIP at site 324 (rather than the existing VIP at site 104). This mayoccur because, e.g., client 102 is physically closer to site 324 thansite 104.

Upon receiving the DNS response, client 102 can transmit an applicationrequest packet to the VIP at site 324, which is received by virtualserver 330 (step (7), reference numeral 320). Virtual server 330 canperform its designated processing on the request packet (e.g., loadbalancing, compression, etc.) and redirect the packet to one ofapplication servers 332, 334, and 336 on host system 328 (step (8),reference numeral 322). The receiving application server can thenprocess the request packet per the logic of application A, generate aresponse, and cause the response to be returned, either directly orthrough virtual server 330/ADC 326, to client 102 (not shown).

With the AI cloning mechanism shown in FIG. 3, ARB 124 can automaticallycreate new application infrastructure and offload application traffic tothe new infrastructure on an as-needed basis (e.g., in response to loador resource failures), without requiring significant intervention by auser/administrator. For example, in one embodiment, the only input auser/administrator may need to provide to ARB 124 is (1) the policy forcontrolling when AI cloning is triggered, and (2) the location ofhardware resources for creating a new infrastructure. This enables theapplication service provider to quickly adapt to changing trafficdemands/requirements and ensure stable application performance.

Although not shown in FIG. 3, in certain embodiments the AI cloningmechanism can also tear down a cloned application infrastructure once itis no longer needed (e.g., when load at the original site subsides).This tear down flow is described with respect to FIG. 5 below.

5. Detailed ARB Workflows

FIG. 4 depicts a flowchart 400 provides additional details regarding theprocessing that may be performed by ARB 124 to carry out AI cloningaccording to an embodiment. At block 402, ARB 124 can monitor loadand/or health metrics pertaining to the infrastructure for anapplication at a first site (e.g., site 104 of FIG. 3). For example, ARB124 can monitor load and/or health metrics pertaining to virtual server116, ADC 112, application servers 118-122, and/or host system 114.

At block 404, ARB 124 can determine whether the monitored metrics exceed(or fall below) one or more predefined thresholds. For instance, in thecase where ARB 124 monitors the number of concurrent connections to theVIP of virtual server 114, ARB 124 can determine whether this numberexceeds a predefined connection threshold. The thresholds may be definedin a policy created by a user/administrator of ARB 124.

If the metrics have not crossed any thresholds, flowchart 400 can returnto block 402 and ARB 124 can continue its monitoring.

On the other hand, if one or more thresholds are crossed, ARB 124 canidentify a second site (e.g., site 324) that has unused/excess ADC andhost capacity. In one embodiment, if there are multiple potential sites,ARB 124 can select a site that is most likely to improve applicationperformance (e.g., the site that is physically closest to the accessingclients, the site that has the most free resources, etc.).

Once identified, ARB 124 can clone a new virtual server (with a new VIP)for the application on an ADC at the second site based on the originalvirtual server at the first site (block 408). As part of this process,ARB 124 can copy any configuration information pertinent to the virtualserver from the first site to the second site.

Further, ARB 124 can clone new application servers for the applicationon a host system at the second site based on the original applicationservers at the first site (block 410). Like the virtual server, as partof this process, ARB 124 can copy any configuration informationpertinent to the application servers from the first site to the secondsite. In embodiments where the application servers run within VMs, block410 can specifically comprising cloning the VMs via known techniquesthat are supported by the host system hypervisors at the first andsecond sites.

At blocks 412 and 414, ARB 124 can configure the new virtual server topoint to the new application servers at the second site and can save arecord of the cloning operation. Finally, ARB 124 can send anotification comprising the new VIP and an application identifier (e.g.,host name) to a GSLB (e.g., GSLB 108), thereby enabling the GSLB toredirect new traffic for the application to the new infrastructure atthe second site.

As noted previously, in certain embodiments ARB 124 can also dynamicallytear down a cloned application infrastructure. FIG. 5 depicts aflowchart 500 of such a process according to an embodiment. Flowchart500 assumes that ARB 124 has created a new application infrastructure ata second site (per flowchart 400 of FIG. 4) due to high load at a firstsite.

At block 502, ARB 124 can continue to monitor the load of the virtualserver and/or application servers at the first site. Further, at block504, ARB 124 can check whether the load has fallen below a predefinedload threshold. In one embodiment, this predefined load threshold may bespecified in the same user-defined policy discussed with respect toblock 404 of FIG. 4. In alternative embodiments, the predefined loadthreshold may be specified in a separate user-defined policy (e.g., a“tear down” policy).

If the load at the first site has not fallen below the load threshold(indicating that the demand at the first site remains high), flowchart500 can return to block 502 and ARB 124 can continue its loadmonitoring.

On the other hand, if the load at the first site has fallen below theload threshold, ARB 124 can conclude that the new infrastructure at thesecond site is no longer needed. As a result, ARB 124 can dismantle thecloned infrastructure at the second site (block 506). In a particularembodiment, this can comprise (1) freeing the hardware (e.g., ADC andhost system) resources associated with the virtual server andapplication servers at the second site, and (2) deleting theirassociated configurations.

Finally, at block 508, ARB 124 can send a notification to GSLB 108 toremove the new VIP from its list of IP addresses associated with theapplication, which will cause future application traffic to be directedback to the VIP at the first site.

6. Exemplary Computer System

FIG. 6 depicts an exemplary computer system 600 according to anembodiment. In one embodiment, computer system 600 can be used toimplement management server 106 of FIGS. 1-3. As shown in FIG. 6,computer system 600 can include one or more processors 602 thatcommunicate with a number of peripheral devices via a bus subsystem 604.These peripheral devices can include a storage subsystem 606 (comprisinga memory subsystem 608 and a file storage subsystem 610), user interfaceinput devices 612, user interface output devices 614, and a networkinterface subsystem 616.

Bus subsystem 604 can provide a mechanism for letting the variouscomponents and subsystems of computer system 600 communicate with eachother as intended. Although bus subsystem 604 is shown schematically asa single bus, alternative embodiments of the bus subsystem can utilizemultiple busses.

Network interface subsystem 616 can serve as an interface forcommunicating data between computer system 600 and other computingdevices or networks. Embodiments of network interface subsystem 616 caninclude wired (e.g., coaxial, twisted pair, or fiber optic Ethernet)and/or wireless (e.g., Wi-Fi, cellular, Bluetooth, etc.) interfaces.

User interface input devices 612 can include a keyboard, pointingdevices (e.g., mouse, trackball, touchpad, etc.), a scanner, a barcodescanner, a touch-screen incorporated into a display, audio input devices(e.g., voice recognition systems, microphones, etc.), and other types ofinput devices. In general, use of the term “input device” is intended toinclude all possible types of devices and mechanisms for inputtinginformation into computer system 600.

User interface output devices 614 can include a display subsystem, aprinter, or non-visual displays such as audio output devices, etc. Thedisplay subsystem can be a cathode ray tube (CRT), a flat-panel devicesuch as a liquid crystal display (LCD), or a projection device. Ingeneral, use of the term “output device” is intended to include allpossible types of devices and mechanisms for outputting information fromcomputer system 600.

Storage subsystem 606 can include a memory subsystem 608 and a file/diskstorage subsystem 610. Subsystems 608 and 610 represent non-transitorycomputer readable storage media that can store program code and/or dataused by, e.g., ARB 124 of FIGS. 1-3.

Memory subsystem 608 can include a number of memories including a mainrandom access memory (RAM) 618 for storage of instructions and dataduring program execution and a read-only memory (ROM) 620 in which fixedinstructions are stored. File storage subsystem 610 can providepersistent (i.e., non-volatile) storage for program and data files andcan include a magnetic or solid-state hard disk drive, an optical drivealong with associated removable media (e.g., CD-ROM, DVD, Blu-Ray,etc.), a removable flash memory-based drive or card, and/or other typesof storage media known in the art.

It should be appreciated that computer system 600 is illustrative andmany other configurations having more or fewer components than shown inFIG. 6 are possible.

The above description illustrates various embodiments of the presentinvention along with examples of how aspects of the present inventionmay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present invention as defined by thefollowing claims. For example, although certain embodiments have beendescribed with respect to particular process flows and steps, it shouldbe apparent to those skilled in the art that the scope of the presentinvention is not strictly limited to the described flows and steps.Steps described as sequential may be executed in parallel, order ofsteps may be varied, and steps may be modified, combined, added, oromitted. As another example, although certain embodiments have beendescribed using a particular combination of hardware and software, itshould be recognized that other combinations of hardware and softwareare possible, and that specific operations described as beingimplemented in software can also be implemented in hardware and viceversa.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. Other arrangements,embodiments, implementations and equivalents will be evident to thoseskilled in the art and may be employed without departing from the spiritand scope of the invention as set forth in the following claims.

What is claimed is:
 1. A method comprising: monitoring, by a computersystem, one or more metrics pertaining to an infrastructure for anapplication at a first site, wherein the infrastructure includes a firstvirtual server and a plurality of first application servers, and whereinthe first virtual server is configured to receive, at a first virtual IPaddress (VIP), client requests for the application and redirect theclient requests to one or more of the plurality of first applicationservers; and if the one or more metrics exceeds or falls below one ormore corresponding thresholds, cloning, by the computer system, theinfrastructure at a second site distinct from the first site, therebyenabling the application to be hosted at the second site, wherein theone or more thresholds are specified in a cloning policy defined by auser.
 2. The method of claim 1, wherein the first virtual server ismaintained by a first application delivery controller (ADC) at the firstsite.
 3. The method of claim 2, wherein cloning the infrastructure atthe second site comprises: identifying a second ADC at the second site;and creating, on the second ADC, a second virtual server for theapplication based on the first virtual server.
 4. The method of claim 3,wherein the first ADC maintains configuration information for the firstvirtual server, and wherein creating the second virtual servercomprises: copying the configuration information from the first ADC tothe second ADC; and associating the copied configuration informationwith the second virtual server.
 5. The method of claim 3, whereincloning the infrastructure at the second site further comprises: causingthe second virtual server to redirect traffic destined for a second VIPto one or more of a plurality of second application servers at thesecond site.
 6. The method of claim 2, wherein the one or more metricsinclude a load or health metric for the first ADC.
 7. The method ofclaim 6 wherein the load or health metric for the first ADC is a CPU ormemory utilization of the ADC.
 8. The method of claim 1, wherein theplurality of first application servers run within virtual machines (VMs)hosted on one or more first host systems at the first site.
 9. Themethod of claim 8, wherein cloning the infrastructure at the second sitefurther comprises: identifying one or more second host systems at thesecond site; and creating, on the one or more second host systems, aplurality of second application servers for the application based on theplurality of first application servers.
 10. The method of claim 9,wherein creating the plurality of second application servers comprises:cloning the VMs running the plurality of first application servers. 11.The method of claim 1, wherein the one or more metrics include a load orhealth metric for the first virtual server.
 12. The method of claim 11wherein the load or health metric for the first virtual server is anumber of concurrent connections to the first VIP.
 13. The method ofclaim 1, wherein the one or more metrics include a load or health metricfor the plurality of first application servers.
 14. The method of claim13 wherein the load or health metric for the plurality of firstapplication servers is a runtime status of the plurality of firstapplication servers.
 15. The method of claim 1, further comprising,subsequently to cloning the infrastructure at the second site:transmitting, to a global server load balancer, a notification that thesecond site is available for hosting the application.
 16. The method ofclaim 15, wherein the notification includes a second VIP associated witha second virtual server created at the second site and a host name ofthe application.
 17. The method of claim 1, further comprising,subsequently to cloning the infrastructure at the second site:monitoring a load metric of the infrastructure at the first site; and ifthe load metric falls below a threshold, dismantling the clonedinfrastructure at the second site, such that the application can nolonger be hosted at the second site.
 18. A non-transitory computerreadable medium having stored thereon program code executable by aprocessor, the program code comprising: code that causes the processorto monitor one or more metrics pertaining to an infrastructure for anapplication at a first site, wherein the infrastructure includes a firstvirtual server and a plurality of first application servers, and whereinthe first virtual server is configured to receive, at a first virtual IPaddress (VIP), client requests for the application and redirect theclient requests to one or more of the plurality of first applicationservers; and if the one or more metrics exceeds or falls below one ormore corresponding thresholds, code that causes the processor to clonethe infrastructure at a second site distinct from the first site,thereby enabling the application to be hosted at the second site,wherein the one or more thresholds are specified in a cloning policydefined by a user.
 19. A computer system comprising: a processor; and anon-transitory computer readable medium having stored thereon executableprogram code which, when executed by the processor, causes the processorto: monitor one or more metrics pertaining to an infrastructure for anapplication at a first site, wherein the infrastructure includes a firstvirtual server and a plurality of first application servers, and whereinthe first virtual server is configured to receive, at a first virtual IPaddress (VIP), client requests for the application and redirect theclient requests to one or more of the plurality of first applicationservers; and if the one or more metrics exceeds or falls below one ormore corresponding thresholds, clone the infrastructure at a second sitedistinct from the first site, thereby enabling the application to behosted at the second site, wherein the one or more thresholds arespecified in a cloning policy defined by a user.